Biomedical subjects

Lionel G Ripley

Publications and source records attributed to Lionel G Ripley.

5 recordsLinked to original sources

PubMed2006

A new and effective tension-band braided polyester suture technique for transverse patellar fracture fixation.

OBJECTIVES: Concerning the tension-band principle of internal fixation, this study aims to establish whether any difference in interfragmentary gap exists after bone-reducing forceps are released, when a recommended suture-knot technique and a new technique are tested in vitro on a purpose built machine that features a model of a transverse fracture of the patella. In addition, a standard tension-band wiring technique has also been tested as one form of control. BACKGROUND: Satisfactory compression at a fracture site reduces the risk of failure of fixation, loss of reduction (interfragmentary gap >2mm) and subsequent risks of malunion, delayed union, and ultimately non-union from excessive movement. Stainless-steel wire can provide a stable rigid construct but is associated with complications. Tension-band fixation employing a braided polyester non-absorbable suture provides a less rigid construct. However, satisfactory clinical results and fewer complications are reported. The method by which a suture is tied has an effect on initial compression provided the fracture is reduced. However, it also has an effect on the degree of fracture gap once it is subject to biomechanical distraction. METHODS: By measuring the output of a strain gauge Wheatstone bridge of a purpose built rig that had been calibrated against fracture gap and compression force, the various tension-band fixation techniques as discussed above were evaluated. RESULTS: The tension-band suture technique examined in this work (the modified Wagoner's Hitch) has been evaluated. It has quantitatively shown less fracture gap than other recognised tension-band suture and wire techniques. The results exhibit statistical significance (p<0.001). CONCLUSIONS: This evaluation study has produced quantitative and comparable data of fracture gap as observed with the model of a transverse patella fracture, for both new and established surgical techniques. The contribution this study has made to the knowledge of the subject is that a testing device similar to the one in this study may be useful in the future for conducting preliminary studies of new or established tension-band techniques. The proposed tension-band suture method tested in this dissertation provided statistically significant quantitative data, which may after further work, support its use as an alternative method in the clinical setting.

Bone Wires↗

PubMed2005

Keeping plaster casts dry: what works?

Plaster casts are commonly used in the management of fractures. The mechanical properties of plasters are adversely affected by water. There are a number of commercial products available to allow patients to continue to shower and swim by protecting the plaster. The aim of this study was to compare these products with a plastic bag and elastic band. Each protector was tested in a shower, immersed in a swimming pool and worn while swimming. The volume of water intrusion was measured. There was no significant difference between a plastic bag and the commercially available products. We do not recommend the use of commercially available plaster protectors for showering or swimming: a plastic bag and elastic band is a cheaper and more convenient device.

Activities of Daily Living↗

PubMed2004

Orientational contrast sensitivity and chromatic contrast thresholds in multiple sclerosis.

PURPOSE: To investigate abnormalities of orientational contrast sensitivity (CS) and chromatic contrast threshold (CCT) in multiple sclerosis (MS). DESIGN: Case control study. METHODS: Nine subjects (mean age, 42 +/- 11 years; range, 20-62 years) with MS, an expanded disability status scale of 3 or less, and normal visual acuity (VA) (logarithm of the minimum angle of resolution [logMAR] VA less than.1) in the tested eye were age-matched with 20 controls. Achromatic CS and CCT were measured using static, computer-generated sinusoidal gratings displayed on a high-resolution monitor. The CS and CCT of each subject were determined using a randomized double-staircase reversal algorithm; CS was measured at five spatial frequencies with horizontal orientation and three with vertical orientation; CCT was measured along the red-green and tritan confusion axes. The sensitivity thresholds of subjects were examined in relation to the mean sensitivity of controls for each spatial frequency. RESULTS: Two subjects had loss of horizontal and vertical CS, and three had isolated vertical loss. When compared with the control mean, there were significant reductions in red-green (P =.016) and tritan (P =.016) discrimination thresholds. CONCLUSION: This study used a computerized psychophysical test designed to minimize many of the test errors associated with earlier studies. It provides confirmatory evidence that MS may be associated with a loss of orientational CS and color vision, in the absence of reduced VA.

Adult↗

PubMed2004

Screening for sight-threatening diabetic retinopathy: comparison of fundus photography with automated color contrast threshold test.

PURPOSE: To compare tritan contrast threshold (TCT) with fundus photography in screening for sight-threatening diabetic retinopathy (STDR), before significant visual loss. DESIGN: Prospective, comparative study. METHODS: A total of 510 consenting diabetic patients attending a hospital-based photographic screening clinic were recruited over a 2-year period. Exclusion criteria included visual acuity of worse than 6/9, previous photocoagulation, and a history of previous eye disease known to affect color vision. The automated TCT test was performed using a computerized cathode ray tube-based technique. Retinal photography was performed using a Polaroid mydriatic fundus camera with a 45 degrees field. Grading of diabetic retinopathy was carried out by an ophthalmologist using slit-lamp biomicroscopy and a 78-diopters lens. Assessments of sensitivity, specificity, and predictive values for both fundus photography and the TCT test were made. RESULTS: Both the fundus photography and TCT test correlated significantly with the presence of STDR (P <.0001, chi(2) test). The TCT test yielded a sensitivity of 94% (95% confidence interval [CI], 73%- 100%) and a specificity of 95% (95% CI, 92%- 96%) for detection of STDR compared with a sensitivity of 88% (95% CI, 66%-97%) and a specificity of 95% (95% CI, 93%-97%) with fundus photography. Combined modality improved overall screening performance. CONCLUSION: The TCT assessment is an effective and clinically viable technique, in comparison with fundus photography, to screen for STDR among a diabetic population. Additionally, our results also showed that combining the TCT test with fundus photography greatly increases the performance of screening for STDR.

Adolescent↗

PubMed2003

Monocular chromatic contrast threshold and achromatic contrast sensitivity in children born prematurely.

PURPOSE: To study the effect of prematurity on monocular chromatic contrast thresholds (CCT) and achromatic contrast sensitivity (ACS). DESIGN: Case-control study. METHODS: A prospective study of 59 children born at less than 33 weeks' gestation was undertaken. Subjects were identified during routine neonatal screening for retinopathy of prematurity and recalled for testing at age 7 to 13 years. Five had stage 1 retinopathy of prematurity, seven had stage 2, and three had stage 3. Sixty-eight full-term children were recruited as controls. Those with major cerebral or eye disease were excluded. The CCT and ACS were measured monocularly in the eye with better visual acuity using static, computer-generated, sinusoidal gratings, displayed on a high-resolution monitor. The CCT and ACS were determined using a randomized double-staircase reversal algorithm. The ACS was measured at five spatial frequencies (0.22, 0.44, 0.88, 1.75, and 3.50 cycles/degree), and the CCT was measured along red-green and tritan confusion axes. RESULTS: Red-green (P =.326) and tritan (P =.910) contrast thresholds and ACS (P >.394 for all spatial frequencies) were similar to the control group. CONCLUSIONS: Previous research suggests that prematurity adversely affects color vision and ACS. This study used a computerized psychophysical test that minimized the test errors inherent in many previous studies. Unexpectedly, CCT and ACS were found to be similar to full-term children.

Adolescent↗